Sewing machine motor controller



Sept. 11, 1945. c R SCHENK 2,384,772

SEWING MACHINE MOTOR CONTROLLER Filed May 26, 1943 r SW um MM 6W5 19.535mg Patented Sept. 11, 1945 2,384,772 sawmc. MACHINE MOTOR CONTROLLERcm R. Schenk, Union, N. 1., assignor toThe Singer Manufacturing Company,Elisabeth, N. J., a corporation of New Jersey Application May 28, 1943,Serial No. 488,551

4 Claims;

This invention relates to foot operated rheostats or controllers, of thecarbon pile type, used to control small motors such as electric sewingmachine motors. One of the objects of this invention is to provide asimplified and improved carbon pile controller or rheostat which can bemanufactured at low cost, is of compact construction and may be readilymanufactured and assembled.

Another object of this invention is to provide an improved manuallycontrolled mechanism for compressing the carbon pile and to arrange themechanism to effect a gradual and uniform variation in the resistance ofthe carbon pile over the entire working range of the manually controlledcompressing mechanism.

With the above and other objects in view, as will hereinafter appear,the invention compr ses the devices, combinations, and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingof a preferred embodiment of the invention, from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

In the accompanying drawing,

Figure 1 is a longitudinal vertical sectional view taken through therheostat and showing, in side elevation. the operating mechanism and thebase on which it is carried.

Fig. 2 is a top plan view of the rheostat with the cover removed.

Fig. 3 is a left end elevation of the rheostat as viewed in Fig. 2.

Referring to the rheostat shown in the drawing, the'hollow casing. inwhich is housed the carbon-pile and the mechanism for compressing it.comprises a hollow top or cover member Iii and a bottom or base memberii, each of which is preferably made of insulating material such asartificial resin, or Y'Bakeilte." The casing is fully shown anddescribed in my prior Patent No. 2,117,257, dated May 10, 1938, to whichreference may be had for a more complete and detailed description.

Formed on the upper face of the base ii is an upstanding substantiallyrectangularly 'shaped block I! formed with a semi-circularly shapedgroove I! (Fi 3) which receives a rheostat comprising a tubularporcelain body it which houses a pile of carbon disks II. The porcelaintube It is adiustably secured in the groove I! by a sheetmetal strap IIwhich has one end overlying the porcelain tube and its other end fixedto the block "by the screws ll.

At one end of the tube ll there is secured a cap il through whichextends the usual conducting pressure head II which is lightly engagedby one end of an L-shaped spring 20, the other end of the spring beingsecured to an upstanding lug it carried by the base Ii. A boss 23 isformed on the base ii, and imbedded in the boss and base is a verticallyarranged pivot pin 24 on which is pivotally mounted a member 25 having acam face 28. Actuating mechanism is provided for swinging the member 25about its pivat N. This mechanism comprises a pull rod 28 having one ofits ends secured to the member 25 and its other end secured at 29 to athree arm lever Ill which is fulcrumed at 3i on the ears 32 of a plateII fixed to the base ll. The cover II is formed with'a rectangularopening or guideway in which is fitted a manually operable push button34 bifurcated at its lower end to receive the ends of a cross-bar SIcarried by the operating arm of the lever 30. The above describedactuating mechanism for the pivoted member 25,

is old and well known and is fully disclosed in my prior Patent N0.2,117,257 previously referred to.

From the above it will be observed that when the push button 34 isdepressed the lever 30 is caused to move about its fulcrum 3i and thuscause the pull rod 28 to swing the member 25 about its pivot 24 in aclockwise direction as viewed in Fig. 2. In order to return the memberII to its normal position, and to maintain the parts in the positionshown in full lines in Fig. 2 when the button 34 is released, a tensionspring I! is provided, said spring having one of its ends secured to therod 28 at the po nt 28 and its other end secured to an upstanding lip 38struck up from the sheet metal strap It.

It will be observed in Fig. 2 that the member 25 does not engage thespring 20 when the parts of the actuating mechanism are in their normalor ineffective position. When the button 34 is depressed the initialmovements of the member 2! about its pivot causes the slightprotuberance 38, formed on the member 25, to engage or contact thespring 20 thereby closing the circuit through the carbon pile. 1

When the point 88 engages the spring 20 the circuit is as follows: fromthe lead A to an L- shaped conductor post 40 which embraces the pivotpin 24, through the pivot pin, the member 2!, spring 20, conductingpressure head It, the carbon pile I, the lead ll which has one of itsends connected to one end of the pile of carbon disk and its other endconnected to an L-shaped conductor bracket 2 which is fixed to the basei I by the screws 43, and thence to the lead D.

Further downward movement of the push button 34 causes the member 25 toswing further about its pivot in a clockwise direction and as thismovement progresses the cam face moves along the spring and decreasesthe effective length of the spring until the member reaches the positionshown in dotted lines in Fig. 2. When the dotted line position shown inFig. 2 is reached, the end of the member remote from the pivotal pointoverlies the conducting pressure head II and the maximum pressure isapplied to the carbon pile, at this point the protuberance H on themember 25 engages a spring 45 carried by the conductor bracket 42 andthe carbon pile is shorted out of the circuit. When the protuberance 44contacts the spring 45 the circuit established is as follows: from thelead A through conductor post 40, pivot pin 2, member :5, spring 65,conductor bracket 42 and thence to the lead D. From the foregoing itwill be observed that during the operation of my improved rheostat thepoint of contact between the cam edge 18 of the member 25 and the spring20 moves back and forth longitudinally of the spring 20 therebyincreasing or decreasing the effective length of the spring and thusvarying the pressure applied to the carbon pile. It is well known inthis type of rheostat that the resistance of the carbon pile decreasesrapidly when pressure is first applied and that the initial pressures onthe pile must be low and applied very gradually. To accomplish thisdesirable result a low tension spring 20 has been used and the member 25has been so located and arranged that the spring 20 is initially flexedat a point remote from the pressure head is in order to take advantageof the maximum resilience of the spring and thus apply the minimum ofpressure to the carbon pile for the initial increments of movement ofthe member 25. As the movement of the member 25 in a clockwise directioncontinues the point of application, to the spring 20, of the flexingforce applied by the cam 26, travels towards the point of contact of thespring 20 with the carbon pile and, therefore, the pressure exerted bythe spring increases a greater amount than would be the case if thepoint of application of the flexible force remained stationary relativeto the spring. It will be understood that the initial pressure of thespring 20 on the carbon pile can be adjusted by loosening the screws Hand sliding the carbon pile longitudinally, thus determining the maximumelectrical resistance of the carbon pile and the minimum speed of themotor controlled thereby. It will also be understood that the shape ofthe cam surface 26 may be varied to give the desired characteristics tothe controller or rheostat and that the form, construction, andarrangements of the other elements employed are susceptible of materialvariation. Therefore,

the privilege is reserved of resorting to all such legitimate changestherein as may be iairly embodied within the spirit of the accompanyingclaims.

Having thus set forth the nature of the invention, what I claim hereinis:

1. A controller for electric motors comprising a base, a carbon pileresistor secured to said base, and means for applying pressure to saidcarbon resistor, said means including a flat spring having one of itsends secured to said base and its other end in electrical contact withsaid carbon pile, a pivoted member having a cam shaped edge, andmanually controlled mechanism for swinging said member about its pivotto cause its cam edge to engage the spring intermediate its ends andmove along said spring towards the end 0! the spring which is in contactwith the carbon pile.

2. A controller for electric motors comprising a rectangularly shapedbase, a carbon pile resistor carried at one side of said base, a flatspring having one of its ends fixed to the other side of the base andextending across said base into contact engagement with the carbon pileresistor, a member pivoted to said base and formed with a cam edge, andmechanism for moving said member about its pivot to cause the cam edgemember to engage the spring intermediate its ends and to travel alongthe spring toward the resistor for the purpose of varying the pressureon the carbon pile resistor.

3. A controller for electric motors comprising a rectangularly shapedbase, a' carbon pile resistor carried at one side of said base, a flatspring having one of its ends fixed to the other side of the base andextending across said base into engagement with the carbon pileresistor, a mem ber pivoted to said base and formed with a cam edge,said cam edge being normally out of contact with said spring, mechanismfor moving said member so that its cam edge engages the springintermediate the ends of the latter and then rolls over the springtowards the carbon pile resistor.

4. A controller for electric motors comprising a base, a carbon pileresistor carried by said base, a flat spring having one end fixed tosaid base and its other end in engagement with said carbon pile, saidcarbon pile being located on one side of said spring, a member locatedentirely on the other side of said spring and adapted to swing about avertical pivot, said member having a cam shaped edge, and manuallycontrolled means for swinging said member about its pivot and caus ingsaid member to engage and roll over said spring in the longitudinaldirection thereof to thereby vary the eifective length of said springfor the purpose of varying the pressure on the carbon pile.

CARL R. SCHENK.

